Jaw-dropping news tonight: the Daily Mail’s James Chapman reveals that Patrick Rock, the deputy director of the Number 10 policy unit and a long-serving political ally of David Cameron, has resigned after being arrested on child porn charges.

Rock was one of Cameron’s Downing Street fixers. The two had worked together as SPADs to Michael Howard and Rock was very much part of the old special adviser network. So, when Cameron and Ed Llewellyn, Cameron’s chief of staff, were looking for a trusted hand to beef up the domestic side of the Downing Street operation they turned to their old colleague, Rock.

Rock’s influence in Downing Street had ebbed slightly in recent months. Jo Johnson had been brought in over his head to run the Policy Unit.

But Rock, as someone who had known Cameron for more than twenty years, still had considerable influence. His departure in any circumstances would have been a blow to Cameron. In these particular circumstances, though, it is a particularly bitter one.

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Tags: Conservatives, David Cameron, Downing Street, Number 10, Patrick Rock, UK poliitcs, UK politics